The field of the present invention is rear suspensions for motor vehicles. More particularly, the invention relates to features of rear suspensions which facilitate the installation (marriage) of a rear axle assembly onto a vehicle body in a properly aligned condition. This invention also relates to the methods which are used to install a rear axle assembly onto a vehicle body.
One type of rear axle assembly commonly used in front wheel drive vehicles is a twist axle. Twist axles are mounted to the underbody of a vehicle at a pair of pivot points defined by bushings. The bushings are typically disposed at an end of axle trailing control arms. The axle trailing control arms typically extend rearward from the bushings. The bushings define an axle pivot axis about which the axle assembly pivots after being mounted on the vehicle. The bushings are typically formed in three primary parts: a generally donut-shaped isolator portion formed of elastomeric material; a cylindrical inner sleeve disposed within and bonded to the isolator; and a cylindrical outer sleeve disposed over and bonded to the isolator. The bushings help to dampen axle impact loads, particularly fore/aft impact loads. The bushings can have different spring rates in each fore/aft direction, the vertical direction and the lateral direction. A transverse beam connects the trailing control arms to form an H-shaped structure. Spring seats are commonly provided on the axle assembly trailing control arms to support suspension coil springs disposed between the body and the axle. Shock absorbers having one end attached to the trailing control arms and a second end attached to the body are also provided. Depending on the structure of the trailing control arms, a transversely-oriented track bar may or may not be placed between the axle assembly and the body to laterally stabilize the axle assembly. Depending on the desired torsional stiffness of the axle assembly, the axle assembly may or may not have a transversely-extending stabilizer bar disposed within or in close proximity to the transverse beam. The stabilizer bar, if utilized, can be of a desired torsional stiffness established by vehicle design criteria.
Each side of the axle assembly has a spindle mounting plate towards a rear end of the respective trailing control arm. The spindle mounting plates may form part of the spring seats. The spindle mounting plates can also be located elsewhere, such as at the extreme ends of the transverse beam, separate from the spring seats. Spindle assemblies, which include wheel bearings, and spindles are mounted to the spindle plates. The spindles rotate relative to the spindle plates. Rotating brake elements, such as brake drums or brake discs, are in turn mounted to the spindles. The wheels are also mounted to the spindles, over the brakes. Because the wheels are mounted, albeit indirectly, to the spindle plates, the spindle plates must be made parallel to each other to facilitate wheel alignment. Also, features on the spindle plates which locate the spindle assemblies thereon must be aligned so that, when mounted, the spindles are axially aligned with each other. The location of the axis of alignment between the spindles is preferentially parallel to the pivot axis of the axle assembly as defined by the sleeves of the bushings, so as to aid in ensuring wheel alignment.
It should be readily apparent that it is critical to align the axle in general and the spindle plates in particular, with the vehicle body to ensure correct wheel alignment. Correct location of the spindle plates relative to the body can help compensate for small errors in locations of the bushings relative to the spindle plates, and in small errors in the locations of the mounting features for the bushings on the body. The axle assembly is fixed relative to the body in a fore/aft location by the fixing of the bushings to the body. The bushings are clamped into place.
Intermediate brackets may be used to connect the bushings to the body. Such brackets provide further opportunity for misalignment. The brackets have side walls (commonly referred to as ears) which define lateral or transverse gaps receiving the axle bushings. The bracket side walls have apertures receiving mounting bolts. The shank of the mounting bolt passes through the aperture and the sleeve of each bushing. The bolt is torqued to clamp the bracket against the sleeve to prevent its rotation. Relative rotation between the axle assembly and the vehicle body is absorbed by the elastomeric isolators.
Typically, in known systems, different locating features are used to locate or position the axle relative to the vehicle body. Separate features, commonly referred to as locator points, are used to position the axle assembly in the fore/aft direction with respect to the vehicle body. Other features on the axle assembly are used to position the axle assembly in the vertical direction. And still other features are used in the lateral direction on each side of the axle assembly to locate each side of the axle to a desired vertical position. It is therefore desirable to commonize the features which locate the axle assembly to the vehicle body.
To make manifest the above-delineated and other desires, the revelation of the present invention is brought forth.
The axle assembly positioning system of the present invention relies on the V notches in the spindle plates as a single feature which provides both a desired fore/aft location or alignment and a desired vertical location or alignment of the spindle plates with respect to a supporting tool tray.
Prior to mounting in the vehicle, the axle module is placed on a supporting tool tray. The tool tray is aligned with the overhead vehicle body. The tool tray has a vertical pin or pins which are aligned with body gauge holes that are penetrated into the rail of the vehicle body forward of the rear wheel wells to insure that the tool tray is aligned with the vehicle body in a fore/aft position and in a lateral position. The tool tray has a plurality of features disposed thereon which engage and support the axle in a desired position. The tool tray (which is a part of a conveyor system) is maintained in fixed fore/aft and lateral positions with respect to the vehicle body during the marriage process. The tool tray additionally has a pair of axle assembly alignment pins axially aligned on an alignment pin axis of a predetermined diameter which engage the V notches in the spindle plates. In one embodiment of the present invention, the diameter of the alignment pins is ⅝ inch. The alignment pins are tangentially engaged by the sides of the spindle plate V notches. The pins position the spindle plates, and thus, the spindles, at a predetermined distance from an upper surface of the tool tray. The tangential engagement of the axle assembly alignment pins with the V notches of the spindle plates also results in positioning the axle assembly at a predetermined fore/aft location relative to the tool tray. The axle assembly alignment pins are axially aligned along an alignment pin axis. The axle assembly alignment pins are held in position relative to the tool tray by support pins (or stands) welded to both the alignment pins and the tool tray. Other locating pins are also provided on the tool tray. A forward pin engages each bushing retention sleeve at approximately the center of the sleeve. The forward pin is of a relatively small diameter to ensure that the pin contacts the sleeve, and not part of the arm. The length of the forward pin relative to the distance of the alignment pin above the tool tray controls the angle of the axle trailing control arms relative to the tool tray. There is also two pair of lateral locating pins. These laterally entrap each trailing control arm of the axle assembly to ensure alignment of the bushings with the brackets.
In the marriage process, the body and the axle assembly are brought together while the axle assembly remains supported by the tool tray. With the position of the axle assembly controlled by the tool tray and the locating pins, the axle assembly is lifted to the desired position relative to the body. The mounting bolts are passed through the apertures in the brackets, through the sleeves and torqued to a predetermined magnitude of torque to clamp the sleeves into place. Once the axle assembly is mounted into place, the tool tray is dropped away from the axle and the body. The axle assembly is connected with the body in a proper fore/aft and lateral aligned position, as well as in a proper xe2x80x9ccurbxe2x80x9d vertical position due to the V notch tangential contact with the axle assembly alignment pins.
Other features and desires of the present invention can be discovered by a review of the accompanying drawings and detailed description of preferred embodiments.